Rodrigue Savoie

Infrared Study of the Crystalline Monohydrates of Nitric, Perchloric, and Sulfuric Acids

The infrared spectra of the solid monohydrates of three strong acids nitric, perchloric, and sulfuric were measured down to 50 cm—1. The last two are completely ionic, viz., H3O+ClO4— and H3O+HSO4—, but the first one always seems to retain a trace of covalent structure, HNO3·H2O. In the three hydrogen‐bonded lattices the H3O+ ions have libration frequencies of the order of 700 cm—1 and translation frequencies lying between 120 and 400 cm—1. The frequencies of these lattice modes increase with the strengths of the hydrogen bonds. The deuterated hydrate of sulfuric acid gave only vitreous spectra because of supercooling. Likewise the room‐temperature phase of perchloric acid monohydrate showed broad, diffuse absorption bands due to the disordered orientation of the hydronium ions. The pyramidal configuration of the H3O+ ion is confirmed definitely.

Raman and infrared spectra of methylmercury complexes of adenine

Abstract The i.r. and Raman spectra of four crystalline methylmercury complexes of adenine have been recorded. Three of these complexes, substituted or coordinated at positions N9, N7/N9, and N3/N7/N9, have well-characterized crystal structures. The last one is probably N6/N7/N9-metalated. The spectra of these complexes, as well as those of adenine, are compared in an attempt to establish correlations between these spectra and the sites of complexation in the derivatives.

Vibrational Spectra of Liquid and Crystalline CF4

The Raman and infrared spectra of CF4 have been recorded in its liquid and two crystalline phases. In the liquid, rotational wings along side some of the fundamentals and the appearance of some forbidden infrared bands reveal the high degree of molecular disorder characteristic of this phase. Very little change occurs in the spectra at the liquid–solid transition; the spectra of Phase I thus appear to be those of a plastic crystal. Marked changes are observed upon cooling to Phase II. The splitting of the fundamentals in the Phase II spectra of CF4 is best interpreted in terms of a S4 tetragonal structure, with the molecules lying on sites of S4 symmetry.

Raman spectroscopic study of the interaction of metal ions with pyridine and maleimide — models for nucleic acids

Abstract Raman spectroscopy was used to study the interaction of various monovalent, divalent and trivalent metal cations with pyridine and maleimide in aqueous solution. The results show that transition-metal ions interact extensively with the nitrogen donor in pyridine. With maleimide, metal binding by the nitrogen atom with displacement of the proton occurs with ions such as Hg2+, Ni2+ and Zn2+. Other ions such as Cu2+, La3+ and Mg2+ cause the deprotonation of maleimide and interact with the resulting enolate anion. Ag+ and Cd2+ ions share both modes of interaction. Relevant conclusions from this study are extended to the special case of metal binding by double-stranded DNA.

Ionic complexation of N2O4 by 18-crown-6

Abstract An ionic complex has been obtained from N 2 O 4 in the presence of the macrocyclic ether 18-crown-6. This crystalline compound has been shown from its Raman spectrum to have the formula NO + ·crown·H(NO 3 ) 2 − , with the nitrosonium ion closely associated with the crown ether rather than with the hydrogen dinitrate accompanying ion. This adduct decomposes readily in moist air to give the known complex (HNO 3 ·H 2 O) 2 ·crown.

Raman spectroscopic study of Ni2+–DNA interactions in aqueous systems

The interactions of Ni2+ ion with calf thymus DNA has been studied in water at metal/DNA phosphate mole ratios ranging from 0.0125 to 6 using Raman spectroscopy. The weighted difference spectra method has been applied to analyze the data. It has been established that Ni2+ ion coordinates mainly at N7 centers of guanine (G) and adenine (A) of DNA at GG, AA and GA sequence places. At the same time the Ni2+ shows outer-sphere interaction, via water molecules, with phosphate groups of DNA.

Aqua complexes of 18—crown-6 with H3PO4, H2TiF6, and HNO3: synthesis and vibrational spectra

Abstract Neutral-component complexes of 2:3:1 (acid:water:18-crown-6) stoichiometry have been obtained with H3PO4 and H2TiF6. These adducts have been studied by infrared and Raman spectroscopy, along with the corresponding (HNO3-H1O)2-18-crown-6 complex, whose synthesis has already been reported. The spectra indicate that the crown ether has a highly regular conformation in these complexes. In those with H3PO4 and HNO3, the binding of the acid molecule to the ether takes place through a H2O linker, the strength of the XOH⋯OH2 hydrogen bond being directly related to the pKa of the acid. With HNO3, the acidic proton appears to be delocalized between the two oxygen atoms, giving a pseudo H2O+ ion whereas in the corresponding deuterocompound the D atom remains associated with the acid.

Multisample System for Raman Difference Spectroscopy

A new type of sample holder suitable for Raman difference spectroscopy is described. It can accommodate up to six different samples (∼10 μL) contained in capillary cells such as those commonly used in conventional Raman spectroscopy. This system can be readily incorporated in an instrument equipped with a conventional computerized control system and it provides a differential frequency accuracy (±0.03 cm−1) which is comparable to that of other existing devices.

Raman Spectra of Liquid and Crystalline ClCN and BrCN

Raman spectra of liquid and solid ClCN and BrCN have been recorded at various temperatures down to 77°K. Shoulders on the low‐frequency side of the stretching fundamentals in the spectra of the liquids are believed to arise from associated molecules. The spectra of the solids are consistent with the reported crystal structures, and polarization effects in a BrCN single crystal have allowed an unambiguous assignment of all the bands in the Raman spectrum.

Fourier transform Raman spectroscopy in the visible region

Low-resolution (ca. 4cm−1) Raman spectra of various liquids and solids, excited by an argon laser at 448 and 514.5 nm, were recorded using a BOMEM DA3.02 commercial interferometer. These spectra were compared with those obtained in the same experimental conditions on a conventional dispersive spectrometer. It is concluded that for low-resolution Raman studies with excitation in the visible region, the dispersive method is superior to the interferometric technique.